Appliance for adjusting and working iris diaphragms of photographic cameras.



'IAIENTED NOV. 19. 1907.

A. WATKINS & G. G. WOODHEAD. APPLIANCE FOR ADJUSTING AND WORKING IRIS DIAPHRAGMS OF PHOTOGRAPHIC CAMERAS.

APPLICATION FILED A114. 1905.

UNITED STATES PATENT OFFICE.

ALFRED WATKINS AND CHARLES G. WOODHEAD, OF HEREFORD, ENGLAND.

APPLIANCE FOB ADJUSTING AND WORKING IBIS DIAPEBGIS OF PHOTOGBAI HIO OAIEBLS.

Specification of Letters Patent.

Patented NOV. 19, 1907.

To all whom it may concern:

Be it known that we,'Ar.rnnn Wa'rxms and CHARLES Gonr'anr Woommsn, 'both subjects of the King of Great Britain, residat Imperial Mills, Hereford, in the'county of ereford, England, have jointly invented certain new and useful Improvements in Apliances for Adipsting and Working Iris 'aphragms of .hotographic Cameras of which the following is a s ification.

In the specification of atkins U. S. Patent No. 681,087 dated 20th August 1901 are described means of adjustin and working shutters and diaphragms of photographic cameras by means of a pair of slides ad ustable relatively to eafih qitherihthe one inillcatin or o erati t e is a iance an d the dither ggnnected t?) tli siiiu t r timin mechanism.

e present invention relates to the ap lication of such slides for a similar purpose ut in conjunction with iris dia hragms and to a modified use of the said sli es.

To effect the first object it is necessary that the area of the iris opening through which the light asses should vary in the same proportion f dr e ual amounts of rotary movement given to t e iris plate slide, and in connection with this, the iris plate slide may be furnished with a logarithmic scale which is to be used in connection with the scales referred to in the above specification. This may be accomplished in a number of ways, as for examp e, with the usual device for opening and closing the leaves of the diaphragm, the effective part of the edges of the leaves may be so shaped as to give t e required result. Or the ordinary ins diaphragm may be used and a suitable movement llnk inte osed between the iris plate slide and the diaphraghm leaves to vary the speed of movement of t e latter in such a manner as will produce the required result ,the result aimed at bein that equal movements of the iris plate will ouble or halve the area of the iris aperture.

In the accompanying drawings Figures 1 and 2 are diagrams lllustrating one means of carrying the invention into effect by suitably shaping the diaphra m leaves; Figs. 3 and 4 illustrate a modifier method in which the movement of ordinary diaphragm leaves is regulated to produce the same result; and Fi 5 and 6 are views of a lens mount provi ed with the slides used in connection with this invention, and Fig. 7 is a diametrical sectional view of a lens mount such as shown in Fig. 5 showing the application of the method 0 re lating the ins opening which is illustrated in F' 3 and 4.

The first method is illustrated in 1 and 2 which show how the shape of the effective part of the leaves is arrived at.

In 1 the diaphragm leaves are pivoted at O and have P1118 such as a movable in radial guide slots A in the iris plate 1. Suecessive equiangular positions of one such 'de slot are s own at A, B, C, D, E, F, G,

corresponding to the varying areas of an iris diaphra usually designated F, F, F, F", F, F, F respectively, the correspon glfpositions of the pin of one diaphragm le being shown at a, b, c, d, e, f, g,

is the center of the aperture and O R the radius of the maximum aperture, corresponding to F Fig. 2 shows the geometrical construction by which the curve of the effective part of the iris leaf is obtained, that is to sa that portion of the edge of the leaf whic contributes to the formation of the iris opening to a greater or less extent according to the extent of the openin In this figure 0 represents the pivot o the iris leaves, and it represents the pin of one leaf, these two parts bein in the same relative position as in Fig. 1. ith O as a center and a distance as radius equal to the distance between 0 and O in Fig. 1, the circle X is drawn. Then with a as center and with radii equal to the distances between 0 and a, b, c, d, e,f, g, and h, respectively, in Fig. 1, circles are drawn which intersect the circle X in the points a, b, c, d, e, f, g, and h, respectively. with these points as centers a series of circles are drawn having radii equal to the distance 0 R in Fig. 1 multiplied respectively by 5.6 5.6 5.6 5.6 5.6 5.6 8 11 16 22 32 45 64 The curve tangential to these circles is then drawn as in Fig. 2, and this curve forms the effective part of the edge of the leaf, the remainder of which may be completed as shown.

An iris diaphragm having its leaves formed as above described will fulfil the condition that e ual angular movements of the iris plate produce a constant rate of variation required.

atcd, will thus form an a of. the iris area, successive equal. displacements of the iris plate doubling or halving the previous aperture area according to the direction of motion of the iris plate, because when the pin a is moved by the radialguide slot into the various equiangular positions shown in Fig. 1, viz. a, b, c, d, e, f, g, h, the center of the aperture and the leaf are moved in relation to one another, the leaf occupying the successive positions indicated in Fig. 2 in each of which the effective part of the edge of the leaf is tangential to a circle of the size A number of such leaves, symmetrically disposed and symmetrically actuaccording to the requirei law.

Figs. 3 and 4 illustrate one method of varying the movement of the-curved leaves of an ordinary iris dia hragm, so as to fulfil the same condition. l ii Fig. 3 the angles between the radial lines show the successive angular displacements of the iris plate I (Figs. 3, 4 and 7) corresponding to the required rate of change of the area of the a erture. If now, there is added to the iris p ate I an additional plate or ring K, having a part of its inner edge formed as a cam (as in Fig.

4) cut to the logarithmic scale of angular displacements shown in Fig. 3 that is to say the successive increments measured along the equally spaced radial lines F"", F, F", F', F, F, F, in ig. 4, are proportional to the successive angular distances between the radial lines F, F, F", F, F", F", F F in Fig. 3, so that for e ual angular displacements in the iris plate as indicated by the radial lines in Fig. the corresponding displacements of the iris leaves about their pivots will be as indicated by the radial lines in Fig. 3, when a pin it fixed to one of the iris leaves is constrained, as for example 1) means of a spring I (Fig. 7) which tem s to keep the iris open, to move along this cam when the iris plate is rotated, the movement of the iris leaves is thereby varied during equal angular displacements of the iris plate so as to make the area of the aperture vary at the requiredconstant geometrical rate for successive equal angular displacements of the iris [plate- With such an iris diaphragm it W0l1l( be unnecessary to provide se arate scales showing the diaphragm va ues corresponding to lenses of different foci or to the separate elements of a compound lens, such for example as might be used either as a doublet lens or with the rent or back combinations by themselves. A single scale would sufl'ice for all these lens systems, the values for each lens being indicated by aseparate index or pointer.

An arrangement of lens mount illustrating the manner of utilizing the iris slide and scale for calculating exposures is shown in Figs. 5 & 6, which are respectively side and front elevations of such a mount. Four SI( 0 by side,

rture which varies scales of values usuall employed in such calculations, P, A, E, 1%, correspomling respectively to plate speed, actinic light value, ex osurc and diaphragm value, are arranged A, E, bein revoluble and rovided with pointers J, I, which traverse t 1c scales P, 1), respectively. The revolving scale E is the iris plate slide controlling the iris aperture in the manner hereinbefcre described, the scale A being simply a plain .revoluble ring. The pointers v having been set respectively to the scale values corresponding to the speed of the plate and the diaphragm to be used, and the actinic value of the light having been estimated or obtained by actinometer, the exposure is given by the value on scale E corresponding to the actinic value so formed as read on scale A. In Fig. 5 the apparatus is set for a plate speed of 128 and a diaphragm value F", and the correct exposure, for example, for actinic value 1 is 1/64th of a second. Obviously the order. in which the scales are placed may be altered in many ways, as by interchanging scales A, E, or scales P, I), or otherwise.

The various scales are shown onthe pcripheries or edges of the slides ordisks, but obviously they may be arranged on the faces of concentric rings or disks.

Having thus described the nature of this invention and the best means we know of carrying the same into practical effect, we claim 1. In combinatibn with an iris diaphragm, a movable member connected therewith which is displaced by equal amounts when the area of the iris aperture is varied at a constant rate.

2. In combination with an iris diaphra m, a movable member connected therewith, and means connecting the diaphragm and movable member, whereby the area of the iris aperture is doubled or halved, according to the direction of movement, for equal dis placements of the movable member.

3. The combination of an iris diaphragm, a rotating member actuating the iris leaves, and means connecting the actuating member with the iris leaves, whereby equal dis lacements of the said actuating member ouble or halve the iris area, according to the direction of rotation of the actuating member, substantially as describei 4. In an iris diaphragm, which is actuated by a'niovable member, an iris leaf having its effective edge shaped to alter the iris area by doubling-or halving, according to the direction of motion of the "actuating member, when thesaid actuating member is displaced by er ual amounts.

5. The herein described improvement in diaphragm mechanism, comprising means for varying the area of the diaphragm opening, a rotatable operating element therefor,

two of them, in this case scales and means whereby equal angular moveequal displacements of the movable memments of said 0 erating element will effect ber.

equal division 0' multi Mention of said area, In testimony whereof we have signed our for the purpose spec-i ed. names to this specification in the presence of 5 6. In combination with an iris diaphragm, two subscribing witnesses.

a movable member connected therewith, and ALFRED WATKINS.

means for jointly operating the diaphragm CHAS. G. WOODIIEAD.

and movable member, whereby the area of Witnesses:

the iris aperture is doubled or halved, 110- Z. T. PEAT,

i0 cording to the direction of movement, for JAMES PARKER. 

